1. Field of the Invention
The present invention relates to a half-bridge LLC resonant converter with a synchronous rectification function, and more particularly to a controller installed at a secondary winding for directly controlling a first synchronous rectifier and a second synchronous rectifier as well as directly controlling a first switch and a second switch of the half-bridge LLC resonant converter with a synchronous rectification function. In addition, the present invention uses a first synchronous rectifier and a second synchronous rectifier with a low conducting resistance to substitute a general rectifier and also greatly lower the power consumption.
2. Description of the Related Art
As a prior art half-bridge LLC resonant converter with a synchronous rectification function usually sets a controller and a switch at a primary winding and a rectifier at a secondary winding, the controller can directly control the electrical conduction or cutoff of the switch. If it is necessary to use the synchronous rectifier, then a transformer or an optical coupler will be used for connecting a control signal to the secondary winding for the control. However, the foregoing prior art half-bridge LLC resonant converter with a synchronous rectification function has the following shortcomings: 1. When the rectifier is conducted electrically, the rectifier consumes much power; 2. The controller cannot control the synchronous rectifier directly; 3. The MOS switch and the rectifier are conducted electrically with each other, and thus it cannot achieve a precise control and the whole circuit may be damaged easily.
In view of the foregoing shortcomings, we need a half-bridge LLC resonant converter with a synchronous rectification function that sets the controller at a secondary winding. Besides controlling the first synchronous rectifier and the second synchronous rectifier directly, the half-bridge LLC resonant converter also can control the half-bridge LLC resonant converter with a synchronous rectification function of the first switch and the second switch directly. Further, the present invention uses the first synchronous rectifier and the second synchronous rectifier with a low conducting resistance to substitute a general rectifier and greatly lower the power consumption, so as to overcome the shortcomings of the prior art half-bridge LLC resonant converter with a synchronous rectification function.